The purpose of this investigation is to study the regulation of intracellular protein degradation in E. coli. In the course of studies designed to obtain a cell-free degradation system from lysozyme-prepared extracts it was discovered that lysozyme itself has limited capacity to hydrolyze proteins and therefore influence apparent degradation in such extracts. Lysozyme-induced proteolysis has been studied using E. coli glutamine synthetase as a substrate in order to partially characterize the essential features of the protein-protein interaction required for hydrolysis and to evaluate the potential hazard of using lysozyme treatment to prepare cell-free extracts. In addition, studies on intracellular degradation in E. coli have continued. Partial degradation of purified glutamine synthetase has been demonstrated in cell-free extracts derived from a recently isolated catalase-deficient mutant. This strain represents a potential source for isolation and characterization of an intracellular proteolytic system in E. coli. Techniques used in these studies have included polyacrylamide pore gradient electrophoresis, isotopic labeling, chromatographic techniques, autoradiography enzymatic assay of functional proteins.